Islamabad, Pakistan (CNN) -- A bank guard was killed and three people wounded when a suicide bomber attacked a bank in Pakistan's capital Islamabad, a senior police official told CNN.

The bomber tried to enter Silk Bank but was stopped by the guard, Tahir Alam told CNN.

The attacker then detonated his explosives, the police official said.

CNN affiliate GEO TV in Pakistan reported that the head of the bomber was found after the blast, and that he appeared to be 17 or 18 years old. He wore a white shalwar kameez, traditional Pakistani clothing.

A separate explosion took place Monday in the city of Quetta, on Gulistan road close to a police station, GEO reported.

Two people were injured, and police and rescue workers were on the scene, the station said.